Skwiz,
Ready for some new feed??
There is no reason you can't get the springs re-arched and add air springs too. (Air springs are all our coach has in the rear.)
About the Onan, look for a comfortable small engine shop. Onans are used lots of places that people want reliable small engines and they may be more interested than a Cummins shop.
About the coach, be real ready. If the rubber parts have not been replaced, age will be getting to a lot of them. You have heard about tires (I hope) that 7 years is about it. It is less in hot climates. But there are hoses and belts that also age out. There are three types of hoses that will leave you stuck. (If you are lucky.)
As the brake fluid has probably absorbed moisture, this would be a good time to flush the system. Replacing all the rubber brake lines while you do this is convenient.
The coolant has probably depleted it anti-corrosives, so replacing any coolant hoses that have gotten hard or spongy is easier when the system is already drained.
On this "old" a unit, the rubber fuel lines may not have the sense of humor for today's "motor fuel" and replacing all you can with new alcohol tolerant hose with prevent a lot of future grief.
The three about are not terrible work and if you do it, you will learn a lot and make the reliability of you coach bags better.
The coach in the picture is ours. It is 48yo and has about 180K on the clock. We go where we want to and have been on a hook only for very serious (and unlikely) component failures.
So, give her the care she deserves and she will give you times of great enjoyment.
You might try to find an owners group on the web. If you can, the information they can provide will be of amazing value.
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.